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package com.firefly.codec.http2.encode;

import com.firefly.codec.http2.frame.Flags;
import com.firefly.codec.http2.frame.Frame;
import com.firefly.codec.http2.frame.FrameType;
import com.firefly.codec.http2.frame.PriorityFrame;
import com.firefly.utils.io.BufferUtils;

import java.nio.ByteBuffer;
import java.util.Collections;
import java.util.List;

public class PriorityGenerator extends FrameGenerator {
    public PriorityGenerator(HeaderGenerator headerGenerator) {
        super(headerGenerator);
    }

    @Override
    public List generate(Frame frame) {
        PriorityFrame priorityFrame = (PriorityFrame) frame;
        return Collections.singletonList(generatePriority(
                priorityFrame.getStreamId(),
                priorityFrame.getParentStreamId(),
                priorityFrame.getWeight(),
                priorityFrame.isExclusive()));
    }

    public ByteBuffer generatePriority(int streamId, int parentStreamId, int weight, boolean exclusive) {
        ByteBuffer header = generateHeader(FrameType.PRIORITY, PriorityFrame.PRIORITY_LENGTH, Flags.NONE, streamId);
        generatePriorityBody(header, streamId, parentStreamId, weight, exclusive);
        BufferUtils.flipToFlush(header, 0);
        return header;
    }

    public void generatePriorityBody(ByteBuffer header, int streamId, int parentStreamId, int weight,
                                     boolean exclusive) {
        if (streamId < 0)
            throw new IllegalArgumentException("Invalid stream id: " + streamId);
        if (parentStreamId < 0)
            throw new IllegalArgumentException("Invalid parent stream id: " + parentStreamId);
        if (parentStreamId == streamId)
            throw new IllegalArgumentException("Stream " + streamId + " cannot depend on stream " + parentStreamId);
        if (weight < 1 || weight > 256)
            throw new IllegalArgumentException("Invalid weight: " + weight);

        if (exclusive)
            parentStreamId |= 0x80_00_00_00;
        header.putInt(parentStreamId);
        header.put((byte) (weight - 1));
    }
}